dm writecache: fix typo in name for writeback_wq

The workqueue's name should be "writecache-writeback" instead of
"writecache-writeabck".

Signed-off-by: Huaisheng Ye <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-writecache.c

···
 		goto bad;
 	}
 
-	wc->writeback_wq = alloc_workqueue("writecache-writeabck", WQ_MEM_RECLAIM, 1);
+	wc->writeback_wq = alloc_workqueue("writecache-writeback", WQ_MEM_RECLAIM, 1);
 	if (!wc->writeback_wq) {
 		r = -ENOMEM;
 		ti->error = "Could not allocate writeback workqueue";